I want to know if a 1991 buick regal 3.1l v6 can be made to fit in a 1997 grand prix that currently houses a 3.1l?

the engines are not interchangeable. The 91 is an OBD-I engine, the 97 is OBD-II. The 97 uses two crank sensors, the 91 only one, just to name one of the many differences.

the engines are not interchangeable. The 91 is an OBD-I engine, the 97 is OBD-II. The 97 uses two crank sensors, the 91 only one, just to name one of the many differences.

Ok! Give me a little insight on this. My brother-in-law has the 97 grand prix and I am thinking about buying it from him. What happend is the crankcase filled with antifreeze. I have no idea if it was ran very long when this happened. What are some possible causes and what should I look for when tearing it down?

Ok! Give me a little insight on this. My brother-in-law has the 97 grand prix and I am thinking about buying it from him. What happend is the crankcase filled with antifreeze. I have no idea if it was ran very long when this happened. What are some possible causes and what should I look for when tearing it down?
Intake gaskets are famous for doing that in that motor. All bearings are now shot. It will be a complete overhaul with journals ground, block bored, etc. have the block checked for cracks as well as the heads. It won't be a quickie. Use the redesigned GM intake gaskets and new bolts for intake with threadlocker applied. The P/N will be on the info sheet in the package with the intake gaskets.